This invention relates to charge pump power supplies for use in providing power to circuits or systems, and more particularly to regulated charge pump power supplies.
Efficient power supplies are necessary for providing power to many types of electronic circuits. Switched mode power supplies (SMPS), for example, are used in many applications in consumer and other products including television receivers, personal computers, facsimile machines, video cassette recorders, and computer monitors. These SMPS may be based on flyback transformer technology, but other technologies may be used as well.
Because of the heavy use of these power supplies in high volume consumer applications, standby power consumption is of great importance, since the devices are kept in standby mode most of the time. Additionally, industry standards recommend the permissible standby power consumption levels of such apparatus. Furthermore, again because of the high volume applications for these power supplies, low cost is also a significant factor.
In the past, when SMPS were only operated in a power on mode or turned off, the SMPS controller, which may be a separate integrated circuit, was usually powered from a secondary winding of the output transformer of the SMPS. Later apparatus such as television receivers, computer monitors, and the like required a power supply which could be operated in a standby mode, usually controlled by a microcontroller which was used to sense, for example, an infrared signal from a remote device to turn on the main power supply by providing an enable signal to the SMPS controller.
To achieve the low power consumption required in standby mode, a secondary reconfiguration technique is often used. Instead of disconnecting the loads from the power supply, which would be a very expensive solution because of the cost of the switches and other components needed to perform such an operation, all the secondary windings voltages must be drastically reduced. To do so, the voltage on one of the secondary windings of the power transformer must be pulled down to a level such that the microcontroller can be appropriately supplied. Since the voltage per turn of the output transformer is constant, however, the other output voltages are similarly reduced according to the same ratio. If the SMPS controller were also powered from the output transformer in standby mode as well as in power on mode, the winding voltage reduction in the transformer results in the SMPS controller no longer being properly supplied. To take advantage of the relatively inexpensive reconfiguration technique for standby operation, a cost effective way to supply the SMPS controller must be found.
Presently the problem of supplying power to the microcontroller is solved by the use of a separate, stand alone, low power flyback SMPS dedicated to supplying operating voltage to the microcontroller. While this solution does not require the use of the cost effective reconfiguration technique because if the microcontroller is separately powered the entire power supply, including the SMPS controller, may be turned off awaiting a signal from the microcontroller to resume supplying power, it itself is a somewhat expensive solution because of the cost of the additional components used as well as the area taken up by the additional circuitry on the SMPS circuit board. Accordingly, it is an object of this invention to provide a low cost method and circuit for providing power to an electronic device including, for example, an SMPS controller during standby operation, by providing a charge pump apparatus and a method for operating a charge pump power supply so as to provide regulated power to the electronic device.